The khawarij is a very capable offensive troop. BS13 is high for Haqqislam and even when compared across factions it remains a respectable score. A high BS combined with a standard light infantry movement score of 4-4 results in a troop that is able to travel around the board reasonably quickly and threaten lots of targets.
Khawarijs boast super-jump which allows them to move vertically in the same way they would horizontally. For example, you can use your movement to jump 2" into the air and then 2" back down. It also means that they can safely fall a distance equal to the sum of their MOV values, in this case 8". This is exceptionally useful because it allows you to approach targets from strange angles your opponent hasn't covered with pesky ARO pieces, and it enables you to remove targets that your opponent thinks are safe behind buildings or walls. This is the main unique selling point that khawarijs have.
Another powerful addition to the khawarijs skills is Fatality L2, found on the spitfire profile. It has two effects. The first gives BS weapons +1 damage. So the spitfire would hit with damage 15 instead of 14. The second is it results in the user rolling criticals on not just their target number but rolls of 1 as well. With two different numbers resulting in criticals this means each dice you roll has a huge 10% chance to result in a critical hit - which is brutal. The spitfire itself rolls 4 dice per attack so every single face-to-face has a high chance of resulting in a critical hit (about 35%, assuming your target number isn't 1, so you have two possible numbers resulting in a crit). The spitfire itself gives great coverage from 8" to 24", and really helps the khawarij excel as a mid-range active-turn hunter.
In terms of close combat khawarijs have tricks up their sleeves there too! The poison skill means that every successful close combat hit results in the target having to make a BTS roll against damage equal to the khawarij's PH value (13), in addition to the ARM roll caused by the close combat weapon itself. That's two rolls for every hit! Unfortunately with a CC value of 20 they're not absolute masters of melee, but they are reasonably capable.
Moving to weapons, there are several possibilities for an offensive khawarij. The spitfire has already been discussed. The profile with a rifle and grenades is interesting because a high PH value of 13 means that a khawarij will be throwing grenades in good range on 16s. This can be a really potent option against clustered infantry. It also opens up the chance to use speculative fire with the grenades, which would hit on 10s. Being able to target opposing units from safety and with a reasonable chance of success is extremely helpful. In terms of range bands the grenades and shotgun would give you amazing 0-8" coverage, whilst the rifle would provide good 8-16" coverage.
Finally there's the boarding shotgun and panzerfaust profile. The boarding shotgun packs a punch on a khawarij, hitting on 19s between 0-8" if the opponent isn't in cover, and comes stock with damage 14 and AP ammunition. This can be a real heavy infantry killer. The panzerfaust has a low burst value of 1 so is probably best as an ARO weapon, but it does feature AP+EXP ammunition so using it in the active turn when your opponent's troops have a lowered burst raises the chance of scoring a nasty hit.
Unfortunately this is where the khawarij falls down in a large way. With a very low ARM value of 1, the khawarij is essentially no better at taking hits than a line infantry. Its BTS is also nothing to get too excited about at 3. However the PH value of 13 can help when choosing dodge as an ARO.
Peculiarly the khawarij does come with bioimmunity which renders it immune to the effects of shock and viral ammunition, it just treats them as any other normal hit. However, it can choose to put hits from shock or viral weapons against its ARM or BTS value, which is very useful because the BTS value of a Khawarij is a little higher than its ARM. Honestly this isn't a skill that's useful often, but every now and again it will result in a khawarij going unconscious against shock ammo instead of straight to dead, which could allow you to heal it back up again!
Religious troop can be a bit of a pain defensively. Instead of passing guts rolls to stay in place when you take a hit, you need to pass a guts roll to duck away into cover. This can be a little irritating because it makes it harder for a khawarij to hide after surviving a shot, which essentially means it's more likely to get shot again.
When it comes to weapon options, most loadouts are best suited to the active turn but grenades and panzerfausts can be very nasty ARO weapons. A khawarij with grenades gives you access to a short-range template weapon that hits on 16s if the opponent isn't in cover and is in good range. Whilst a panzerfaust hits on BS16 when the opponent is in good range and out of cover, and has EXP ammunition which forces 3 saves per hit. Of course shotguns have the potential be hitting on 19s and are also template weapons. So the Khawarij definitely does have some good ARO options to think about.
- Remember super jump allows you to jump up buildings you'd normally have to climb up. It allows you to jump across large gaps. It allows you to jump over short walls. Super jump opens up so many new attack possibilities. But do be careful you don't fall! If you run out of movement whilst in the air then you end up falling and that can really hurt!
- Smoke grenades can really help a khawarij survive when using super-jump. The issue super-jump has is that it often exposes you to many AROs. Smoke grenades help this by blocking opposing troops' line of fire so they can't take those AROs. Use this to ensure the khawarij can use super-jump and survive.
- Bioimmunity allows you to ignore the effects of shock and viral rounds, but you can still choose to use your BTS for the save instead of ARM. Doing this is wise because your BTS is higher.
Khawarijs are strong in the active turn and have a few ARO tricks up their sleeves, there's no doubt about it. The panzerfaust option in particular can be very threatening. However it's worth remembering that we are talking about a lightly armoured infantry with no camouflage or hiding abilities and no way to increase its burst when it AROs, bar suppressive fire. Therefore no particular tricks are required to take one out. Approach them from a range you're favoured in and shoot them with a high burst weapon. Alternatively use camouflage and surprise shot to lower their BS to a much lower value.
Most khawarij loadouts suggest a use as a mid-ranged aggressive unit that wants to be in the middle of the board making use of super-jump. There's a lot of inherent risk in this strategy and super-jump in particular can attract lots of unwanted AROs as you elevate yourself above the terrain. In order to support a khawarij smoke grenades and doctors can be a large help. The smoke will block off AROs you don't want to take as you jump, whilst doctors will help to keep the khawarij on its feet. Cheap additions like Ghazi or Ghulam Doctors can make all the difference here, for minimal investment.
It's also worth noting that the khawarij wants to be an aggressive troop but lacks a lot of ways to deal with tricky units such as those with ODD or camouflage. Due to this, taking a khawarij as your only aggressive piece may leave some holes in your list. In order to address this flaw it might be worth thinking about taking direct template weapons like flamethrowers, or troops with MSV that ignore camouflage and ODD modifiers. By doing this you could end up with a more well-rounded list.
When thinking about an aggressive khawarij it's worth bearing in mind that shotguns, rifles, and spitfires want to be relatively close to opposing troops due to their focus on shorter range-bands. Deploying towards the front of your deployment zone can help to bring the khawarij into a good range-band sooner.
Think about the terrain around you and how you can use super-jump to your advantage. You might be able to deploy close to a building that's relatively inaccessible to most troops due to not having a ladder - but you can jump onto the rooftop to take favourable shots. When deploying a khawarij don't just think about where you want to go horizontally, across the board, also consider where you want to go vertically. Maybe you can jump up to one rooftop and then use super-jump to hop from one building to the next whilst avoiding ground-level troops. Thinking about these kinds of moves and planning them as you deploy can be very helpful.
Active Turn Role
As discussed the khawarij is mostly used as an active-turn hunter given its high BS of 13, and the fantastic fatality skill. What this means is that the job of a khawarij is to use superior movement and shooting skills to weed out opposing troops and attack from positions where they're vulnerable. Finding the right spot to strike from is important because a khawarij doesn't take hits very well. Plan a movement carefully. Try to use super-jump to attack from an angle where you deny the opposing troop cover, or perhaps a position where they can't ARO at all. Then execute the plan and go for the kill. Use smoke to block other AROs and be careful about how you approach. When your turn is nearing the end it's probably a good idea to hide away in a safe spot, ready to be activated again in the next turn.
Bear in mind the PH value of a khawarij is equal to their BS (13). There is no shame at all in dodging with a khawarij, and often it's going to be the right decision.
Remember that the spitfire loadout with fatality rolls criticals on 1s as well as the target number. If both dodging and shooting are going to be on the same value then taking the shot is superior because you have a higher chance to roll a critical.